Our major goal is to investigate the role of descending (bulbospinal) neuronal systems in the mediation of opiate analgesia and pain perception. Research efforts for the coming year will be focused in three major experiments: (1) studies on the site of action of opiates in the brain stem with emphasis on the nucleus raphe magnus and nucleus coeruleus (2) examination of the responses of cells in the nucleus raphe magnus and locus coeruleus to various modalities and sites of noxious stimulation; (3) examination of brain stem neuronal substrates acted on in common by opiates and other analgesic agents, such as baclofen (Lioresal).